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31 ; Electrical Research (ID = 634621) Radio
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31 ; Electrical Research (ID = 634621) Radio
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Country:  United States of America (USA)
Manufacturer / Brand:  Electrical Research Laboratories Inc. (Erla); Chicago, Illinois
Year: 1929 Category: Broadcast Receiver - or past WW2 Tuner
Valves / Tubes 8: 24 24 24 27 27 45 45 80
Main principle TRF (Tuned-Radio-Frequency but use of regeneration unknown); Screengrid 1926-1935
Tuned circuits 4 AM circuit(s)
Wave bands Broadcast only (MW).
Power type and voltage Alternating Current supply (AC) / 110 Volt
Loudspeaker Electro Magnetic Dynamic LS (moving-coil with field excitation coil)
Power out
from Model: 31 - Electrical Research
Material Wooden case
Shape Console, Highboy (legs > 50 %).
Notes One dial (primary tuning control knob) ; 4-gang condenser; phono input; push-pull af output stage.
The Rider´s schematic shows type "27" tubes instead of type "24" screen grid tubes (probably an early version of the 224 model).
Price in first year of sale 147.00 $
External source of data Ernst Erb
Source of data Radio Collector`s Guide 1921-1932
Circuit diagram reference Rider's Perpetual, Volume 2 = 1932 (Models 1931/1932)
Mentioned in The Radio Collector's Directory and Price Guide 1921 - 1965

All listed radios etc. from Electrical Research Laboratories Inc. (Erla); Chicago, Illinois
Here you find 131 models, 45 with images and 61 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.